Overview and Types of Colon Polyps

A polyp is a term used to describe a growth on the lining of a mucous membrane. The growth may develop on the lining of the digestive tract, mouth, uterus, bladder, nasal passages, or genital area. When a polyp develops in the colon, it is usually benign (noncancerous). However, in some cases, it can develop into a malignancy (cancer).

Colon Polyps Symptoms
Verywell / Nusha Ashjaee

Identifying Colon Polyps

There are different types of colon polyps, each of which has its own characteristics and structure. These and other factors (including size and location) can help determine if they have a greater potential of developing into colon cancer.

Colon polyps are quite common, with studies reporting that they occur in 30%–50% of adults. They are usually found during a visual examination of the colon. If discovered, the growths can be removed and the tissue is sent to the lab to assess if any abnormalities are suggestive of a malignancy.

The American College of Gastroenterology currently advises that average-risk adults undergo colorectal screening starting at age 45 using one of two techniques:

  • Colonoscopy: A long tube with a small camera is inserted into the rectum and threaded through the colon to visually examine the entire colon.
  • Fecal immunochemical test (FIT): A stool test to detect blood in the stool (a possible sign of cancer).

If you're unable to undergo colonoscopy or FIT or you're looking for alternative options, you may consider one of these secondary screening methods:

  • Flexible sigmoidoscopy: A flexible tube with a camera that can only detect polyps in the last portion of your colon.
  • FIT-DNA test (also known as a multitarget stool DNA test): A stool test, such as Cologuard, that looks for the presence of blood and abnormal DNA from cancer cells or polyps.
  • Virtual colonoscopy (also known as CT colonography): Uses a type of CT scan to get images of the colon without requiring sedation or full insertion of a scope. However, it is not as sensitive as a standard colonoscopy.
  • Colon capsule endoscopy: You swallow a capsule with a micro-camera to get images of the digestive tract and colon.

While adults age 45 to 75 are advised to undergo colorectal cancer screening, those age 76 to 85 should first check with their doctor, as screening is decided on an individual basis.

Shape

When describing a polyp, a doctor may use terms to describe its shape. These physical descriptions help the doctor determine how to deal with a polyp should it need to be removed. They also provide insights into its potential for cancer.

Colon polyps typically come in two basic shapes:

  • Sessile polyps: Sit on the surface of the mucous membrane. They are flat or dome-shaped and do not have a stalk.
  • Pedunculated polyps: Raised, mushroom-like growths that are attached to the surface of the mucous membrane by a long, thin stalk (peduncle).

Pedunculated polyps are easier to spot because they are raised. By contrast, sessile polyps lie flat on the surface and are more likely to become cancerous simply by virtue of being missed.

Types

Beyond their physical appearance, the doctor will want to determine what type of polyp it is. This typically requires examining the tissue under a microscope to look at both the structure and characteristics of the cells themselves. Among the more common classifications:

  • Inflammatory colon polyps: They are mostly found in people with inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis. Inflammatory polyps are sometimes referred to as pseudopolyps ("false polyps") because they aren’t polyps per se but rather an inflammatory manifestation of IBD. These polyps are benign and are unlikely to become cancer.
  • Hyperplastic polyps: These are defined by the activity of cells in the tissue mass. Hyperplasia ("fast growth") simply means that there is an abnormal increase in the numbers of cells resulting in the growth of a polyp. Despite their rapid growth, hyperplastic polyps are unlikely to become cancerous. (An enlarged prostate is another example of benign hyperplasia.)
  • Adenomatous polyps (or adenomas): They make up about two-thirds of all polyps found in the colon. While adenomas can become cancerous, most do not. Unlike hyperplastic polyps, adenomas are neoplastic. Neoplasia ("new growth") is a term used to describe an abnormal growth of cells that gradually lose the characteristics of normal cells. When neoplastic cells form into a mass, we refer to that as a tumor. A neoplasm can be benign, malignant, or something in between.
  • Villous Adenoma: This is a type of adenomatous polyp that has a greater potential of becoming cancerous. It is estimated that around 30% of villous adenomas will develop into a malignancy. These polyps often have cauliflower-like protrusions and may require surgery to remove.

Any polyp with a villous component or a length greater than 1 cm, regardless of the type, is typically removed since it is considered high risk for becoming cancer. Common removal techniques include using a wire loop known as a LEEP or an electrocautery device that burns the polyp at its base.

Symptoms

For the most part, you probably won’t know if you have polyps. You generally can’t feel them, and they are usually only found during a colorectal screening. If symptoms do appear, they may include:

  • Changes in bowel habits, including constipation or diarrhea
  • Rectal bleeding or blood in stools (bright red or dark, tarry stools)
  • Unexplained weight loss
  • Abdominal pain (rare)

If this combination of symptoms persists for more than a week, make an appointment to see your doctor.

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